Metadata-based bypassing in a controller

ABSTRACT

Provided are a computer program product, system, and method for data unit classification in accordance with one embodiment of the present description, in which in response to a data processing command, a storage controller classifies data units of a storage unit as either allocated to a data set or as unallocated to any data set. If allocated to a data set, the storage controller can further classify data set-allocated data units as either containing client data or metadata or as empty. In accordance with one aspect of the present description, the storage controller may bypass data processing of the data units which have not been allocated to any data set or otherwise do not contain client data or metadata. Other aspects of data unit classification in accordance with the present description are described.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a computer program product, system, andmethod for data processing data units of a data storage unit.

2. Description of the Related Art

In certain computing environments, multiple host systems may configuregroups of data often referred to as “data sets” in storage volumesconfigured in a storage system, such as interconnected storage devices,e.g., a Direct Access Storage Device (DASD), Redundant Array ofIndependent Disks (RAID), Just a Bunch of Disks (JBOD), etc., which aretypically controlled by a storage controller coupled to the hosts andstorage devices. Data sets which may contain a file or many files, aretypically comprised of data units often referred to as “extents,” whichtypically may comprise data stored in groupings of smaller data unitsoften referred to as “tracks.” The Z/OS® operating system fromInternational Business Machines Corporation (“IBM”) has a Volume Tableof Contents (VTOC) to provide to a host, information on data sets ofextents configured in the volume, where the VTOC indicates to the host,the location of tracks, extents, and data sets for a volume in storage.

Various data processing tasks are frequently performed at a storagevolume level. For example, to avoid loss of data, data stored on avolume (often referred to as a primary volume) may be backed up bycopying it to another volume (often referred to as a secondary volume)frequently stored at another geographical location. Accordingly, in theevent that data on the primary volume is lost due to data corruption,hardware or software failure, or a disaster which destroys or damagesthe primary volume, the backup data may be retrieved from the secondaryvolume.

In a typical volume level copying operation by a storage controller, alltracks allocated to the volume are copied, whether or not the trackscontain client data or metadata. In many storage systems, hosts haveaccess to metadata stored in a VTOC identifying which tracks of a volumehave been allocated to data sets and which tracks of a data set containclient data or metadata. Using host software, some analysis may be doneto avoid copying unallocated areas of a volume or unused areas of anon-VSAM (Virtual Storage Access Method) data set. However, such VTOCmetadata has typically not been readily accessible to the storagecontroller. Moreover, for VSAM data sets, both used and unused areaswithin the data set are typically moved by the host software.

SUMMARY

Provided are a computer program product, system, and method for, in oneaspect of the present description, data unit classification forselective data processing by a storage controller. In one embodiment, inresponse to receipt of a command to perform data processing of datastored within a storage unit, such as a storage volume, for example,which is controlled by the storage controller, metadata is read by thestorage controller from a storage unit data structure, and based uponread metadata, data units of the storage unit are classified as dataset-allocated to one or more data sets, or are classified as unallocatedto any data set. In one aspect of the present description, dataprocessing is performed upon data of at least a portion of the dataunits classified as data set-allocated data units of the storage unit,whereas data processing of data units classified as unallocated dataunits, is bypassed.

In another aspect, based upon read metadata, data set-allocated dataunits are classified as data containing data set-allocated data units,or are classified as empty data set-allocated data units. Dataprocessing is performed on data contained by data containing dataset-allocated data units of the storage unit whereas data processing ofthe empty data set-allocated data units is bypassed. Other aspects ofdata unit classification in accordance with the present description aredescribed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates an embodiment of a storage environment, employingaspects of data unit classification in accordance with the presentdescription.

FIG. 1B illustrates another embodiment of a storage environment,employing aspects of data unit classification in accordance with thepresent description.

FIG. 2 illustrates an embodiment of a volume table.

FIG. 3 illustrates an embodiment of a data set record.

FIG. 4 illustrates an embodiment of operations of a storage controlleremploying data unit classification in accordance with the presentdescription.

FIG. 5 illustrates an example of a map of data extents of a storagevolume classified in accordance with one aspect of the presentdescription.

FIG. 6a illustrates an example of data extents of a storage volumeclassified in accordance with another aspect of the present description.

FIG. 6b illustrates an example of data tracks of a storage volumeclassified in accordance with as aspect of the present description.

FIG. 7 illustrates a computing environment in which the components ofFIGS. 1A, 1B may be implemented.

DETAILED DESCRIPTION

A storage unit such as a storage volume may be subdivided into storagesubunits, also referred to herein as data units, such as tracks orextents, for example. Described embodiments provide techniques forfacilitating data processing performance in which a storage controller,in response to a volume level data processing command, for example,classifies data units such as extents or tracks as either allocated to adata set (hereinafter referred to as “data set-allocated data units”) oras unallocated to any data set. In accordance with one aspect of thepresent description, the storage controller may bypass data processingof the data units which have not been allocated to any data set sincethe unallocated data units of the volume do not contain client data ormetadata.

In another aspect of the present description, the storage controller canfurther classify data set-allocated storage units which have beenallocated to a data set of the volume, as either containing client dataor metadata or as empty. Any empty data set-allocated data units maysimilarly be bypassed notwithstanding that the data units have beenallocated to data set because the empty data set-allocated data units donot contain client data or metadata. Conversely, any data set-allocateddata unit classified as containing client data or metadata may beprocessed in accordance with the volume level data processing command.

Thus, upon receipt of, for example, a volume level copy command to copya storage volume, the data units allocated to data sets and actuallycontaining client data or metadata may be copied to another volume.Conversely, copying operations for unallocated data units or dataset-allocated data units which are empty, may be bypassed to increasethe speed or efficiency at which the volume level copying command isperformed. In this manner, data units of a storage unit such as astorage volume may be classified as suitable candidates for volume leveldata processing while other data units of the same storage volume areclassified as suitable candidates for being bypassed to increase dataprocessing efficiency notwithstanding that the candidates for dataprocessing and the candidates for being bypassed may be intermixedwithin a single storage volume.

The illustrated embodiment is described in connection with a dataprocessing command which copies data units from one storage unit such asa storage volume to another storage volume. For example the dataprocessing command may be an instant copy operation performed by thestorage controller. An example of such an instant copy command is an IBMFlashCopy® command modified by data unit classification in accordancewith the present description. However, it is appreciated that data unitclassification in accordance with the present description may be appliedto other types of data processing such as moving, migrating, mirroring,synchronizing or resynchronizing data of one storage unit with respectto another storage unit of the storage system.

Metadata describing the data stored within a storage unit such as astorage volume, may be stored in a storage unit data structure such as,for example, a Volume Table of Contents (VTOC) which is typically storedin the storage volume itself. Previously, the VTOC metadata wasformatted in a manner suitable for the host to read the VTOC and obtainthe metadata stored in the VTOC. In one aspect of the present invention,a storage unit data structure such as a Volume Table of Contents (VTOC)stored in the storage volume may be formatted to be read by the storagecontroller as well as the host, to facilitate data unit classificationfor storage unit level commands such as volume level commands, forexample. As a result, in one embodiment, the data processing candidateclassification and the bypass candidate classification of data unitssuch as extents or tracks stored in a particular storage unit such as astorage volume, as described herein, may be undertaken by the storagecontroller. It is appreciated that in other embodiments, the dataprocessing and bypass candidate classification of groups of data such asdata units as described herein may be undertaken by the host, or acombination of both the storage controller and the host, for example,depending upon the particular application. Accordingly, one or both ofthe host and the storage controller may have logic configured to readthe VTOC of a storage volume and obtain appropriate metadata for dataprocessing and bypass candidate classification.

Once suitable data unit candidates for volume level data processing havebeen identified, the client data or metadata of each suitable candidatemay be located and processed in accordance with the data processingcommand. In many storage controllers, the data of a data set is storedin data extents, each of which may be located in different availablestorage spaces. As a consequence, the data of a single data set may bedispersed over several different storage units such as storage volumes.In accordance with the present description, each storage volume of amultivolume data set has metadata identifying the location of theextents of each data set located within the particular volume, as wellas metadata identifying an open/closed status indicating whether theassociated data set is open for input/output operations or is closed forinput/output operations. In one aspect of the present description, dataprocessing of extents of a data set which is still open for input/outputoperations is deferred until the data set is closed to ensure that alldata of the data set is processed.

Previously, the location of each extent of a data set stored in astorage volume was identified in metadata of the VTOC which wasformatted in a manner to be understandable only to logic of the host. Inaccordance with another aspect of the present description, in oneembodiment, the storage controller may also include logic configured toobtain and process the extent location metadata from the VTOC for eachdata unit found to be a suitable candidate for data processing. As aresult, the storage controller may be configured to read and understandboth the extent location metadata and the open/closed status metadatainformation for each data set having data stored in the storage volume.

Still further, the storage controller may be configured to read andunderstand metadata identifying a boundary in a data set, in which theboundary indicates the end of the data units of the data set containingdata, and the beginning of the data units of the data set which areempty. In addition, the storage controller may be configured to read andunderstand the metadata identifying the locations of the extents whichhave not been allocated to any data set.

Based upon the read metadata, the storage controller is configured toidentify the data units allocated to data sets and which actuallycontain client data or metadata and to identify unallocated data unitsor data set-allocated data units which are empty. Thus, upon receipt of,for example, a volume level copy command to copy a storage volume, thedata units allocated to data sets and actually containing client data ormetadata may be copied by the storage controller to another volume.Conversely, copying operations for unallocated data units or dataset-allocated data units which are empty, may be bypassed by the storagecontroller to increase the speed or efficiency at which the volume levelcopying command is performed. It is appreciated that in otherembodiments, other features and advantages may be realized, in additionto, or instead of those described herein, depending upon the particularapplication.

In one embodiment, a storage unit such as a storage volume, may storedata in subunits of storage which are referred to herein as data unitsor storage subunits. Examples of data units or storage subunits includestorage allocation units, cylinders, tracks, extents, gigabytes,megabytes, etc. the relative sizes of which may vary. For example, astorage allocation unit is typically on the order of 16 megabytes insize or 21 cylinders in size, depending upon the appropriate unit ofmeasure.

As previously mentioned, a data set may comprise many data extents, eachdata extent being stored in a particular storage unit such as a storagevolume. A data extent of a data set typically comprises data stored in aplurality of data units or storage subunits such as tracks which aretypically physically located in physically contiguous storage areas ofthe storage unit. Thus, in the context of storage volumes, each dataextent of a data set typically comprises data stored in a plurality ofphysically contiguous tracks of a particular storage volume. It isappreciated that the size of each storage subunit or data unit may vary,depending upon the particular application. A storage controllertypically processes data in groups of data in integral multiples ofstorage allocation units such that the smallest increment of data beingprocessed is typically no smaller than a single storage allocation unit.It is appreciated that data may be processed in various sizes of dataunits such as tracks, cylinders, megabytes, gigabytes, data extents,allocation units, etc.

In some embodiments, the storage unit such as a storage volume, may be avirtual storage volume having a plurality of virtual data units orstorage subunits of a storage unit. One example of a virtual data unitis a virtual storage allocation unit. Each virtual storage allocationunit is mapped by the storage controller to an actual physical storageallocation unit in a particular storage performance tier. The mapping ofeach virtual allocation unit of each data extent stored in a virtualstorage volume, is typically contained within the metadata for that dataset in the VTOC data structure of the particular virtual storage volume.

FIG. 1A illustrates an embodiment of a computing environment including astorage control unit, such as a storage controller 100 or server, thatmanages access to data sets 102 configured in storage volumes 104 in astorage 106 by one or more hosts as represented by a host 108 (FIG. 1A).The storage controller 100 may be a primary storage controller 100 a(FIG. 1B) for a primary storage 106 a similar to the storage 106 (FIG.1A), or may be a secondary storage controller 100 b for a secondarystorage 106 b similar to the storage 106 (FIG. 1A). The storage volumes104 (FIG. 1A) of the storage devices 106 a, 106 b (FIG. 1A) may be in apeer-to-peer mirror relationship such that data written to one storagevolume, typically a primary storage volume in the primary storage 106 a,is mirrored to a corresponding secondary storage volume in the secondarystorage 106 b such that the secondary storage volume is a copy of theprimary storage volume. The source of the data written to the storagevolumes is typically one or more of the hosts 108. Thus, the hosts 108issue input/output requests to a storage controller 100 requesting thestorage controller 100 to read data from or write data to the storagevolumes 104 of the storage 106 controlled by the storage controller 100.It is appreciated that data unit classification in accordance with thepresent description is applicable to other types of storage units inaddition to storage volumes in a mirrored, peer-to-peer relationship.

A data set 102 (FIG. 1A) comprises a collection of data intended to bestored in a logical allocation of data, such as data from a singleapplication, user, enterprise, etc. A data set 102 may be comprised ofseparate files or records, or comprise a single file or record. Eachrecord or file in the data set 102 may be comprised of data extents ofdata.

The storage controller 100 includes an operating system 110 and dataunit classification control logic 112 to manage the storage of data sets102 in the storage volumes 104 in accordance with the presentdescription. The operating system 110 may comprise the IBM z/OS®operating system or other operating systems for managing data sets instorage volumes or other logical data structures. (IBM and z/OS aretrademarks of IBM worldwide). The data unit classification control logic112 may be separate from the operating system 110 or may be includedwithin the operating system. The data unit classification control logicmay be implemented with hardware, software, firmware or any combinationthereof.

It is appreciated that some or all of data unit classification controlfunctions in accordance with the present description may be implementedin one or more of the hosts 108 as represented by the data unitclassification control logic 120 of the host 108. Here too, the dataunit classification control logic 120 may be separate from the operatingsystem of the host or may be included within the host operating system.The data unit classification control logic 120 may be implemented withhardware, software, firmware or any combination thereof.

Each storage volume 104 includes metadata concerning the data sets 102stored in one or more storage unit data structures of each storagevolume 104 such as a storage volume table 200 having information on thestorage volume 104 to which it pertains, including open/closed statusmetadata, and extent location metadata for each data set 102 having datastored in the particular storage volume 104. The open/closed statusmetadata may be used to classify the status of each data set ascurrently open for input/output operations, or currently closed toinput/output operations active or inactive. The extent location metadatamay be used identify the data extents of each data set 102, and tolocate the physical storage locations of each data extent of the datasets 102 having data stored in the particular storage volume 104.

The storage volume table 200 may be stored in the storage volume 104,such as in the first few records of the storage volume, i.e., startingat the first track in the storage volume 104. In IBM z/OS operatingsystem implementations, the storage volume table 200 may comprise astorage volume table of contents (VTOC). In other embodiments, thestorage volume metadata may include a Virtual Storage Access Method(VSAM) Volume Data Set (VVDS). In one embodiment, the storage volumetables 200 may comprise contiguous space data sets having contiguoustracks or physical addresses in the storage 106. In alternativeembodiments, the storage volume table 200 may comprise a file allocationtable stored separately from the storage volume 104 or within thestorage volume 104. It is appreciated that storage volume metadata mayinclude metadata in other formats describing various aspects of the datasets 102 of the storage volume.

The storage controller 100 may maintain copies of the storage volumetables 200 to use to manage the data sets 102 in the storage volumes104. In z/OS implementations, the storage volume table 200, e.g., VTOC,may include extent location metadata describing locations of data setsin the storage volume 104, such as a mapping of tracks in the data setsto physical storage locations in the storage volume. In someembodiments, the storage volume metadata may include open/closed statusmetadata fields containing data indicating whether the data set iscurrently open for input/output operations or is closed. In someembodiments, the storage volume table 200 may comprise other types offile allocation data structures that provide a mapping of data tostorage locations, either logical, virtual and/or physical storagelocations. In this way, the storage volume table 200 provides a mappingof tracks to data sets 102 in the storage volume 104. In furtherembodiments, the storage volume table 200 may include metadata such as astorage volume name and data set records indicating data sets havingdata extents configured in the storage volume 104. Each data set recordmay have information for each data set 102 in a storage volume 104,including the data units (e.g., tracks, blocks, etc.) assigned to thedata set 102. Tracks may be stored in data extents, which provide amapping or grouping of tracks in the storage volume 104. The storagevolume 104 may further include a storage volume table index 210 thatmaps data set names to data set records in the storage volume table 200.In one embodiment, the metadata may include a mapping of the dataextents of each data set 102 (or data set portion) stored within thestorage volume 104, to physical allocation units which may be identifiedby cylinder and/or track numbers, for example.

The storage 106 may comprise one or more storage devices known in theart, such as a solid state storage device (SSD) comprised of solid stateelectronics, EEPROM (Electrically Erasable Programmable Read-OnlyMemory), flash memory, flash disk, Random Access Memory (RAM) drive,storage-class memory (SCM), Phase Change Memory (PCM), resistive randomaccess memory (RRAM), spin transfer torque memory (STM-RAM), conductivebridging RAM (CBRAM), magnetic hard disk drive, optical disk, tape, etc.The storage devices may further be configured into an array of devices,such as Just a Bunch of Disks (JBOD), Direct Access Storage Device(DASD), Redundant Array of Independent Disks (RAID) array,virtualization device, etc. Further, the storage devices may compriseheterogeneous storage devices from different vendors or from the samevendor.

The storage controller 100 communicates with the storage 106 viaconnection 116. The components of the embodiment depicted in FIG. 1B aresimilarly interconnected by connections 116 a, 116 b . . . 116 n. Theconnections 116, 116 a, 116 b . . . 116 n each may comprise one or morenetworks, such as a Local Area Network (LAN), Storage Area Network(SAN), Wide Area Network (WAN), peer-to-peer network, wireless network,etc. Alternatively, the connections 116, 116 a, 116 b . . . 116 n maycomprise bus interfaces, such as a Peripheral Component Interconnect(PCI) bus or serial interface.

FIG. 2 illustrates an example of an arrangement of informationmaintained in a storage unit data structure such as an instance of astorage volume table 200 _(i) for one storage volume 104 _(i). It isappreciated that metadata for a storage unit in accordance with thepresent description may have other arrangements, depending upon theparticular application.

The storage volume table instance 200 _(i) of this example includes astorage volume name 202, also known as a storage volume serial number,e.g., a VOLSER, that provides a unique identifier of the storage volume.The storage volume name 202 may be included in the name of the storagevolume table 200 _(i) in the storage volume 104 _(i). The storage volumetable 200 _(i) instance further includes one or more data set records300 ₁ . . . 300 _(n) indicating data sets having data extents of tracksconfigured in the storage volume 104 _(i) represented by the storagevolume table 200 _(i). In embodiments where the operating system 110comprises operating systems such as the Z/OS operating system, the dataset records may comprise data set control blocks.

The storage volume table 200 _(i) further includes one or more freespace records 204 identifying ranges of available tracks in the storagevolume 200 _(i) in which additional data set records 300 _(n+1) can beconfigured, or may be allocated to data sets. Thus, the tracksidentified by the free space records 204 have not yet been allocated toa data set for client data or a data set for metadata, and therefore maybe classified as unallocated. In accordance with the presentdescription, these unallocated tracks may be bypassed by the storagecontroller in performing a volume level data processing command and thusneed not be processed in response to the volume level data processingcommand since the unallocated tracks do not contain client data ormetadata.

FIG. 3 illustrates an example of an instance of a data set record 300_(i), such as one of the data set records 300 ₁ . . . 300 _(n) includedin the storage volume table 200 _(i). Each data set record 300 _(i)contains metadata 302, 304, 306, 310 pertaining to a particular data set102 (FIG. 1A). In one embodiment, the metadata may be arranged in fieldsincluding for example, a field 302 identifying a name for the particulardata set, one or more fields 304 identifying the locations of data unitssuch as tracks, extents or storage allocation units, for example, whichhave been allocated to the data set of the record 300 _(i), one or morefields 306 identifying a data boundary address of the data unit whichborders between data units of the data set containing client data ormetadata, and data units of the data set which are empty, that is, donot contain client data or metadata. In addition, one or more fields 310indicate whether the data set of the record 300 _(i) is currently openfor access by input/output operations, or is currently closed forinput/output operations.

Thus, in one embodiment, the allocation of data units such as tracks orextents to a data set having data stored within a particular volume isdescribed within the VTOC on each volume. In one embodiment, the VTOCcontains Format1/Format3 Data Set Control Block (DSCB) chains thatdescribe the extents on the volume that a data set resides within.

As previously mentioned in some embodiments, the storage volume metadatamay include a Virtual Storage Access Method (VSAM) Volume Data Set(VVDS). In some non-VSAM embodiments, a field within the aforementionedcontrol blocks, such as the DS1IND80 field, for example, may be used bythe storage controller to determine whether the particular storagevolume is the last volume containing data for the list of volumes withinwhich a data set occupies. Another field, such as the DS1LSTAR, forexample, may be used by the storage controller to compute a boundaryaddress which identifies where in the list of extents occupied by thedata set, that actual data stops and the empty space begins.

As explained in greater detail below, this metadata may be utilized bythe storage controller to determine which extents and which tracks ofthe extents occupied by a data set actually contain client data ormetadata. Accordingly, in one aspect of the present description, thestorage controller can limit the tracks copied in response to a volumelevel copy command for example, to just those tracks which actuallycontain client data or metadata instead of copying all the tracksallocated to the data set whether or not the data set actually containsclient data or metadata.

For VSAM data sets, it is noted that the VTOC also contains the locationof a data set, the VVDS (Virtual Storage Access Method (VSAM) VolumeData Set) for each volume. In some embodiments, the VVDS is made up ofVSAM Volume Records (VVRs) in which there is a VVR for each VSAM dataset of the volume. The VVR for a data set contains a Data setInformation Cell which in turn defines a High Used Relative Byte Address(HURBA). The storage controller may use the HURBA to determine aboundary address which is the address of the particular track of thetracks allocated to the data set, at which the data-containing tracks ofthe data set end, and the empty data tracks of the data set begin. Heretoo, in one aspect of the present description, the storage controllercan limit the tracks copied in response to a volume level copy commandfor example, to just those tracks which actually contain client data ormetadata instead of copying all the tracks allocated to the data setwhether or not the track actually contains client data or metadata.

As set forth above, the volume table 200 may include metadata 204identifying free space of the storage unit which has not yet beenallocated to a data set. Thus, a VTOC may include, for example a map,such as the VTOC Pack Space Map (VPSM), for example, which maps freeareas of storage that have not been allocated to a data set. The storagecontroller may be configured to read the free space map of the VTOC forpurposes of data unit classification.

It is appreciated that the metadata describing various aspects of thedata set of the record 300 _(i) may include other fields, either inaddition to or instead of those depicted in this example, depending uponthe particular application. The data unit location information 304 maybe expressed as disk, cylinder, head and record location (CCHHR), orother formats, either virtual or physical. Terms such as tracks, dataunits, blocks, storage allocation units, etc., may be usedinterchangeably to refer to a unit of data managed in the storage volume104. The storage volume table 200 may be located at track 0 and cylinder0 of the storage volume 104. Alternatively, the storage volume table 200may be located at a different track and cylinder number than the firstone.

FIG. 4 illustrates an embodiment of operations performed by a data unitclassification logic such as a data unit classification control logic112, 112 a, 112 b, 120 (FIGS. 1A, 1B) in accordance with the presentdescription, in which individual data units of a storage unit such as astorage volume may be separately classified as allocated or unallocated,and empty or data containing, and data processed accordingly in whichunallocated and empty data units are bypassed instead of being dataprocessed. In one operation, the storage controller may receive (block410) a command or instruction to perform a data processing task. In oneembodiment, the command may be to perform a data processing task at astorage volume level such as copying the data of an entire volume.

In accordance with the present description, the storage controller inperforming the volume copying command, can bypass data units of thevolume, which do not contain client data or metadata and insteadrestrict the copying operations to those data units which actually docontain client data or metadata. As a result, the volume level copyingoperation may in some embodiments, be performed more quickly and moreefficiently in some applications. Although described in connection witha volume level data processing command in the embodiment of FIG. 4, itis appreciated that data unit classification in accordance with thepresent description is applicable to other levels of commands such aslevels larger than a storage volume or smaller than a storage volume,for example. It is further appreciated that data unit classification inaccordance with the present description may be applied to other types ofdata processing such as moving, migrating, mirroring, synchronizing orresynchronizing data of one storage unit with respect to another storageunit of the storage system. Also, the data processing command received(block 410) by the storage controller may be received from an externalsource such as a host, or may be internally generated by the storagemanagement system of the storage controller, for example.

In response to the receipt (block 410) of the volume level dataprocessing command, the storage controller reads (block 414) metadatadescribing the data stored in the storage volume which is the subject ofthe received data processing command. As previously mentioned, in theillustrated embodiment, each storage volume 104 (FIG. 1A) includesmetadata concerning the data sets 102 which are contained either whollyor partially, within the particular storage volume 104. The metadata isstored in one or more storage unit data structures of each storagevolume 104, such as a storage volume table 200.

In the illustrated embodiment, the storage unit data structure hasmetadata describing the storage volume 104 to which it pertains,including metadata identifying which extents of the storage volumeremain unallocated, the locations of the extents allocated to each dataset of the volume and the open/closed status of each data set 102 havingdata stored in the particular storage volume 104 of the command.Accordingly, based upon the read metadata for the selected storagevolume, a data unit of the storage volume, such as a storage extent maybe selected (block 418) by the data unit classification control logic ofthe storage controller for classification to determine (block 422) ifthe selected data unit should be classified as allocated to a data setor as unallocated, that is, not allocated to any data set. As previouslymentioned, the storage volume table 200 _(i) (FIG. 4) of each storagevolume 104 includes one or more free space records 204 identifyingranges of available tracks in the storage volume 200 _(i) which have notyet been allocated to a data set including data sets for client data anddata sets for metadata. Thus, the tracks identified by the free spacerecords 204 which have not yet been allocated to a data set may beclassified as unallocated. Conversely, if the selected extent is notwithin the free space tracks identified by the free space records 204,the selected extent may be classified (block 422) as allocated to a dataset.

In another embodiment, the metadata for a storage volume may include amap 510 (FIG. 5) such as a VTOC Pack Space Map (VPSM), for example, inwhich a map element for each data unit such as an extent, for example,indicates whether or not the associated extent has been allocated to adata set. Thus, the map 510 depicts for example, a set of map elements514 a, 514 b . . . 514 g, each representing a data extent. In theexample of FIG. 5, the map elements 514 a-514 e indicate that theassociated data extents represented by the map elements 514 a-514 e haveeach been assigned to a data set and thus each has been allocated to adata set. Conversely, in the example of FIG. 5, the map elements 514f-514 g indicate that the associated data extents represented by the mapelements 514 f-514 g have each not been assigned to a data set and thusthe associated data extents represented by the map elements 514 f-514 gremain unallocated. Accordingly, in one embodiment, a metadata map suchas the map 510 of data units such as data extents or data tracks may beread from the metadata of the storage volume by the storage controllerto determine if a particular data unit such as an extent has beenallocated to a data set. It is appreciated that the manner ofdetermining whether a data unit of a storage unit has been allocated toa data set or remains unallocated may vary, depending upon theparticular application.

Extents which are classified (block 422) as unallocated to any data setmay be bypassed (block 424) by the data processing operation of thereceived instruction (block 410), since extents not allocated to anydata set do not contain client data or metadata in the illustratedembodiment. It is appreciated that the criteria for classifying dataunits as suitable candidates for being bypassed by the volume level dataprocessing instruction may vary, depending upon the particularapplication. Further, although described in connection with extents, itis appreciated that the classification operation of block 422 and thebypass operation of block 424 may be applied at a different level dataunit such as a track, allocation unit, cylinder, etc.

If it is determined (block 422) based upon the metadata read by thestorage controller, that the selected extent should be classified by thestorage controller as allocated to a data set, a further determinationis made (block 432) based upon the metadata read by the storagecontroller, as to whether the data set to which the selected extent hasbeen allocated is to be classified by the storage controller as havingan open or closed status.

In one embodiment, the open/closed status metadata may be used by thedata unit classification control logic of the storage controller toclassify the status of each data set as either open for input/outputoperations, or closed for input/output operations. Because the datacontained with a data set which is open for input/output operations maybe modified as a result of an ongoing input/output operation, in oneembodiment, the open/closed status of a data set may be used to deferthe data processing requested by the received (block 410) command, foran open data set until the data set is closed for input/outputoperations, for example. Thus, in one embodiment, the volume levelprocessing of an extent of a data set open for input/output operationsmay be deferred by selecting (block 418) another extent forclassification. By the time the extents of the data set which was openare subsequently reselected (block 418) for reclassification, the dataset may have closed (block 432). It is appreciated that the criteria forclassifying data units as suitable candidates for deferring the volumelevel data processing instruction may vary, depending upon theparticular application. It is further appreciated that the manner ofdeferring volume level data processing of a data unit allocated to anopen data set may vary, depending upon the particular application.

In one embodiment, a determination (block 432) as to whether the statusof the data set to which the selected extent has been allocated iseither open or closed, may be made by the data unit classificationcontrol logic of the storage controller examining one or more metadatafields 310 (FIG. 3) of a data set record of a Volume Table (FIG. 2) ofthe particular data set to which the selected extent has been allocated.As previously mentioned, the metadata fields 310 indicate whether thedata set of the record 300 _(i) is currently open for access byinput/output operations, or is currently closed for input/outputoperations. It is appreciated that the manner of determining whether thedata set to which the selected extent has been allocated is currentlyopen or closed for input/output operations, may vary, depending upon theparticular application.

If it is determined (block 432) based upon the metadata read by thestorage controller, that the selected extent has been allocated to adata set which is currently closed for input/output operations, theselected extent may be further classified (block 436) based upon themetadata read by the storage controller as to whether the selectedextent is empty, that is, does not contain client data or metadata.Extents which are classified (block 436) as empty may be bypassed (block424) by the data processing operation of the received instruction (block410), since the empty extents do not contain client data or metadatanotwithstanding that the empty extent has been determined to beallocated to a data set in the illustrated embodiment. It is appreciatedthat the criteria for classifying data units as suitable candidates forbeing bypassed by the volume level data processing instruction may vary,depending upon the particular application. Further, although describedin connection with extents, it is appreciated that the classificationoperation of block 436 and the bypass operation of block 424 may beapplied at a different level data unit such as a track, allocation unit,cylinder, etc.

In one embodiment, a determination (block 436) as to whether theselected extent is empty, that is, does not contain client data ormetadata, may be made by the data unit classification control logic ofthe storage controller examining one or more metadata fields 304, 306(FIG. 3) of a data set record of a Volume Table (FIG. 2) of theparticular data set to which the selected extent has been allocated. Aspreviously mentioned, the metadata fields 304 identify the locations ofdata units such as tracks, extents or storage allocation units, forexample, which have been allocated to the data set of the record 300_(i). In addition, the fields 306 identify the location of a boundary inthe form of a data boundary address of the data unit which bordersbetween data units of the data set containing client data or metadata,and data units of the data set which are empty.

For example, FIG. 6a depicts a plurality of contiguous data extents 614a, 614 b . . . 614 g of the storage volume which is the subject of thereceived (block 410, FIG. 4) instruction. The field 304 (FIG. 3) of therecord 300, for the data set of the extent selected (block 422, FIG. 4)for classification, may indicate that the extents allocated to theparticular data set includes extents 614 a-614 e but not extents 614 f,614 g which have not been allocated to a data set. In addition, thefields 306 identify the location of a boundary 620 in the form of a databoundary address of the data unit which borders between data units ofthe data set containing client data or metadata, and data units of thedata set which are empty. As shown in FIG. 6a , the boundary between thedata units containing client data or metadata and the data units whichare empty is a data unit within the extent 614 c in the example of FIG.6 a.

Thus, if the extent selected (block 422, FIG. 4) for classification isone of the extents 614 d or 614 e, for example, the storage controllerby examining the metadata fields 304, 306 (FIG. 3) of a data set recordof a Volume Table (FIG. 2) of the particular data set to which theselected extent has been allocated, can determine that the address ofthe extent 614 d or 614 e selected for classification is beyond theaddress of the extent 614 c containing the data boundary 620. If so, theextent 614 d or 614 e may be determined to be empty, that is, notcontaining client data or metadata, notwithstanding that the extent 614d or 614 e was classified as allocated to a data set. Accordingly, dataprocessing of the data set-allocated, empty extent 614 d or 614 e may bebypassed (block 424) as discussed above, since the data set-allocated,but empty extent 614 d or 614 e does not contain client data ormetadata.

Conversely, if it is determined that the address of the extent selectedfor classification is at or below (that is, to the left of in FIG. 6a )the address of the extent 614 c containing the data boundary 620, theextent may be determined (block 436, FIG. 4) to not be empty, that is,determined to contain client data or metadata. Accordingly, if theselected extent is determined (block 436, FIG. 4) to contain client dataor metadata, another determination (block 440) is made as to whether theselected extent contains the data boundary 620 marking the end of thedata set-allocated data units which contain client data or metadata. Ifan extent selected for classification is determined (block 436) tocontain client data or metadata but does not contain the data boundary620), all data units of the selected extent may be data processed (block448) in accordance with the received (block 410) instruction since alldata units of the selected extent contain client data or metadata.

For example, if the extent selected (block 422, FIG. 4) forclassification is one of the extents 614 a or 614 b (FIG. 6b ), forexample, the storage controller by examining the metadata fields 304,306 (FIG. 3) of a data set record of a Volume Table (FIG. 2) of theparticular data set to which the selected extent has been allocated, candetermine that the address of the extent 614 a or 614 b selected forclassification is below the address of the extent 614 c containing thedata boundary 620. If so, the extent 614 a or 614 b selected (block 422,FIG. 4) for classification may be determined to contain client data ormetadata but not contain the data boundary 620. Consequently, it may bedetermined that all the data units of the selected extent 614 a or 614 bcontain data. Accordingly, data processing is performed (block 444) forall tracks of the extents 614 a or 614 b containing client data ormetadata but not containing the data boundary 629.

In another example, if the selected extent is determined (block 436,FIG. 4) to contain client data or metadata, and if it is determined(block 440) that the selected extent contains the data boundary 620marking the end of the data set-allocated data units which containclient data or metadata, all tracks of the selected extent containingclient data or metadata are processed (block 448) in accordance with thereceived (block 410) instruction. Conversely, all empty tracks of theselected extent lacking client data or metadata are bypassed (block 452)and thus not processed in accordance with the received (block 410)instruction.

In the example of FIG. 6a , the extent 614 c has been allocated to adata set and also contains the boundary 620 between data units whichcontain client data or metadata and those which do not. FIG. 6b depictsa portion of the extent 614 c as represented by a plurality ofcontiguous data track 624 a, 624 b . . . 624 g of the extent 614 c ofthe data set to which the extent 614 c selected (block 422, FIG. 4) forclassification has been allocated. In the example of FIG. 6b , theboundary 620 is defined by the address of the data unit or track 624 ewhich may be stored in a field 306 of a data set record of a VolumeTable (FIG. 2) of the particular data set to which the selected extent614 c has been allocated. Accordingly, the data units or tracks 624a-624 e may be determined to contain client data or metadata since theaddresses of the data units or tracks 624 a-624 e are at or below thatof the address of the data unit 624 e which defines the data boundary620.

Accordingly, tracks 624 a-624 e of the selected extent 614 c are alldetermined to contain client data or metadata and are all processed(block 448) in accordance with the received (block 410) instruction.Conversely, the data units or tracks 624 f-624 g may be determined to beempty, that is not contain client data or metadata since the addressesof the data units or tracks 624 f-624 g are beyond that of the addressof the data unit 624 e which defines the data boundary 620. Accordingly,tracks 624 f-624 g of the selected extent 614 c are all determined to beempty and thus determined to not contain client data or metadata. As aresult, the tracks 624 f-624 g of the selected extent 614 c aretherefore all bypassed (block 452) and thus not processed in accordancewith the received (block 410) instruction.

A determination (block 428, FIG. 4) is made as to whether all extents ofthe storage volume have been classified. If so, the volume level dataprocessing of the received (block 410) instruction has been completed(block 460). Conversely, if extents of the volume remain to beclassified, another extent of the subject storage volume is selected(block 418) for classification, and the data units of the extents areeither data processed in accordance with the data processing of theinstruction or are bypassed, depending upon the classification of theextent or data unis of the extent as described above.

It is seen from the above, that data unit classification for selectivedata processing such as that of volume level commands, can increase thespeed and efficiency of the execution of such volume level commands insome embodiments. It is appreciated that other aspects and advantagesmay be achieved by data unit classification for selective dataprocessing in accordance with the present description, depending uponthe particular application.

Although the operations of FIG. 4 are described in connection with avolume level data processing command for a storage volume, it isappreciated that data unit classification in accordance with the presentdescription may be applied to data processing commands affectingmultiple storage units or volumes or a portion of a single storage unitor volume.

For example, the data of a single data set may be dispersed over severaldifferent storage units such as storage volumes. Thus, data unitclassification for selective data processing in accordance with thepresent description may be applied to multi-volume data sets andmulti-volume level commands and instructions.

It is appreciated that some or all of data unit classification controlfunctions in accordance with the present description as depicted in FIG.4 may be implemented in a storage controller as represented by the dataunit classification control logic 112, 112 a, 112 b of one or more ofthe storage controllers 100, 100 a, 100 b, or in one or more of thehosts 108 as represented by the data unit classification control logic120 of the host 108 (FIG. 1A), or a combination thereof. In oneembodiment, metadata describing a range of storage locations for aparticular storage area may be read by the data unit classificationcontrol logic of the storage controller, for example, and passed toanother data unit classification logic such as the data unitclassification logic 120 of a host 108, for example, for furtherprocessing in accordance with the present description. In one example,the range of storage locations of a particular storage area may bedefined by a CCHH range and volume (or volumes) identification. It isappreciated that the storage locations defining a particular storagearea may be expressed in a variety of different types of data units,depending upon the particular application.

The computational components of FIGS. 1A, 1B, including the controlleror storage controller 100, 100 a, 100 b, host 108, may each beimplemented in one or more computer systems, such as the computer system702 shown in FIG. 7. Computer system/server 702 may be described in thegeneral context of computer system executable instructions, such asprogram modules, being executed by a computer system. Generally, programmodules may include routines, programs, objects, components, logic, datastructures, and so on that perform particular tasks or implementparticular abstract data types. Computer system/server 702 may bepracticed in distributed cloud computing environments where tasks areperformed by remote processing devices that are linked through acommunications network. In a distributed cloud computing environment,program modules may be located in both local and remote computer systemstorage media including memory storage devices.

As shown in FIG. 7, the computer system/server 702 is shown in the formof a general-purpose computing device. The components of computersystem/server 702 may include, but are not limited to, one or moreprocessors or processing units 704, a system memory 706, and a bus 708that couples various system components including system memory 706 toprocessor 704. Bus 708 represents one or more of any of several types ofbus structures, including a memory bus or memory controller, aperipheral bus, an accelerated graphics port, and a processor or localbus using any of a variety of bus architectures. By way of example, andnot limitation, such architectures include Industry StandardArchitecture (ISA) bus, Micro Channel Architecture (MCA) bus, EnhancedISA (EISA) bus, Video Electronics Standards Association (VESA) localbus, and Peripheral Component Interconnects (PCI) bus.

Computer system/server 702 typically includes a variety of computersystem readable media. Such media may be any available media that isaccessible by computer system/server 702, and it includes both volatileand non-volatile media, removable and non-removable media.

System memory 706 can include computer system readable media in the formof volatile memory, such as random access memory (RAM) 710 and/or cachememory 712. Computer system/server 702 may further include otherremovable/non-removable, volatile/non-volatile computer system storagemedia. By way of example only, storage system 713 can be provided forreading from and writing to a non-removable, non-volatile magnetic media(not shown and typically called a “hard drive”). Although not shown, amagnetic disk drive for reading from and writing to a removable,non-volatile magnetic disk (e.g., a “floppy disk”), and an optical diskdrive for reading from or writing to a removable, non-volatile opticaldisk such as a CD-ROM, DVD-ROM or other optical media can be provided.In such instances, each can be connected to bus 708 by one or more datamedia interfaces. As will be further depicted and described below,memory 706 may include at least one program product having a set (e.g.,at least one) of program modules that are configured to carry out thefunctions of embodiments of the invention.

Program/utility 714, having a set (at least one) of program modules 716,may be stored in memory 706 by way of example, and not limitation, aswell as an operating system, one or more application programs, otherprogram modules, and program data. Each of the operating system, one ormore application programs, other program modules, and program data orsome combination thereof, may include an implementation of a networkingenvironment. The components of the computer 702 may be implemented asprogram modules 716 which generally carry out the functions and/ormethodologies of embodiments of the invention as described herein. Thesystems of FIGS. 1A, 1B may be implemented in one or more computersystems 702, where if they are implemented in multiple computer systems702, then the computer systems may communicate over a network.

Computer system/server 702 may also communicate with one or moreexternal devices 718 such as a keyboard, a pointing device, a display720, etc.; one or more devices that enable a user to interact withcomputer system/server 702; and/or any devices (e.g., network card,modem, etc.) that enable computer system/server 702 to communicate withone or more other computing devices. Such communication can occur viaInput/Output (I/O) interfaces 722. Still yet, computer system/server 702can communicate with one or more networks such as a local area network(LAN), a general wide area network (WAN), and/or a public network (e.g.,the Internet) via network adapter 724. As depicted, network adapter 724communicates with the other components of computer system/server 702 viabus 708. It should be understood that although not shown, other hardwareand/or software components could be used in conjunction with computersystem/server 702. Examples, include, but are not limited to: microcode,device drivers, redundant processing units, external disk drive arrays,RAID systems, tape drives, and data archival storage systems, etc.

The reference characters used herein, such as i, j, and n, are used todenote a variable number of instances of an element, which may representthe same or different values, and may represent the same or differentvalue when used with different or the same elements in differentdescribed instances.

The present invention may be a system, a method, and/or a computerprogram product. The computer program product may include a computerreadable storage medium (or media) having computer readable programinstructions thereon for causing a processor to carry out aspects of thepresent invention.

The computer readable storage medium can be a tangible device that canretain and store instructions for use by an instruction executiondevice. The computer readable storage medium may be, for example, but isnot limited to, an electronic storage device, a magnetic storage device,an optical storage device, an electromagnetic storage device, asemiconductor storage device, or any suitable combination of theforegoing. A non-exhaustive list of more specific examples of thecomputer readable storage medium includes the following: a portablecomputer diskette, a hard disk, a random access memory (RAM), aread-only memory (ROM), an erasable programmable read-only memory (EPROMor Flash memory), a static random access memory (SRAM), a portablecompact disc read-only memory (CD-ROM), a digital versatile disk (DVD),a memory stick, a floppy disk, a mechanically encoded device such aspunch-cards or raised structures in a groove having instructionsrecorded thereon, and any suitable combination of the foregoing. Acomputer readable storage medium, as used herein, is not to be construedas being transitory signals per se, such as radio waves or other freelypropagating electromagnetic waves, electromagnetic waves propagatingthrough a waveguide or other transmission media (e.g., light pulsespassing through a fiber-optic cable), or electrical signals transmittedthrough a wire.

Computer readable program instructions described herein can bedownloaded to respective computing/processing devices from a computerreadable storage medium or to an external computer or external storagedevice via a network, for example, the Internet, a local area network, awide area network and/or a wireless network. The network may comprisecopper transmission cables, optical transmission fibers, wirelesstransmission, routers, firewalls, switches, gateway computers and/oredge servers. A network adapter card or network interface in eachcomputing/processing device receives computer readable programinstructions from the network and forwards the computer readable programinstructions for storage in a computer readable storage medium withinthe respective computing/processing device.

Computer readable program instructions for carrying out operations ofthe present invention may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java, Smalltalk, C++ or the like,and conventional procedural programming languages, such as the “C”programming language or similar programming languages. The computerreadable program instructions may execute entirely on the user'scomputer, partly on the user's computer, as a stand-alone softwarepackage, partly on the user's computer and partly on a remote computeror entirely on the remote computer or server. In the latter scenario,the remote computer may be connected to the user's computer through anytype of network, including a local area network (LAN) or a wide areanetwork (WAN), or the connection may be made to an external computer(for example, through the Internet using an Internet Service Provider).In some embodiments, electronic circuitry including, for example,programmable logic circuitry, field-programmable gate arrays (FPGA), orprogrammable logic arrays (PLA) may execute the computer readableprogram instructions by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present invention.

Aspects of the present invention are described herein with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems), and computer program products according to embodiments of theinvention. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer readable program instructions.

These computer readable program instructions may be provided to aprocessor of a general purpose computer, special purpose computer, orother programmable data processing apparatus to produce a machine, suchthat the instructions, which execute via the processor of the computeror other programmable data processing apparatus, create means forimplementing the functions/acts specified in the flowchart and/or blockdiagram block or blocks. These computer readable program instructionsmay also be stored in a computer readable storage medium that can directa computer, a programmable data processing apparatus, and/or otherdevices to function in a particular manner, such that the computerreadable storage medium having instructions stored therein comprises anarticle of manufacture including instructions which implement aspects ofthe function/act specified in the flowchart and/or block diagram blockor blocks.

The computer readable program instructions may also be loaded onto acomputer, other programmable data processing apparatus, or other deviceto cause a series of operational steps to be performed on the computer,other programmable apparatus or other device to produce a computerimplemented process, such that the instructions which execute on thecomputer, other programmable apparatus, or other device implement thefunctions/acts specified in the flowchart and/or block diagram block orblocks.

The flowchart and block diagrams in the Figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods, and computer program products according to variousembodiments of the present invention. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof instructions, which comprises one or more executable instructions forimplementing the specified logical function(s). In some alternativeimplementations, the functions noted in the block may occur out of theorder noted in the figures. For example, two blocks shown in successionmay, in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality involved. It will also be noted that each block of theblock diagrams and/or flowchart illustration, and combinations of blocksin the block diagrams and/or flowchart illustration, can be implementedby special purpose hardware-based systems that perform the specifiedfunctions or acts or carry out combinations of special purpose hardwareand computer instructions.

The terms “an embodiment”, “embodiment”, “embodiments”, “theembodiment”, “the embodiments”, “one or more embodiments”, “someembodiments”, and “one embodiment” mean “one or more (but not all)embodiments of the present invention(s)” unless expressly specifiedotherwise.

The terms “including”, “comprising”, “having” and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

The enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise.

The terms “a”, “an” and “the” mean “one or more”, unless expresslyspecified otherwise.

Devices that are in communication with each other need not be incontinuous communication with each other, unless expressly specifiedotherwise. In addition, devices that are in communication with eachother may communicate directly or indirectly through one or moreintermediaries.

A description of an embodiment with several components in communicationwith each other does not imply that all such components are required. Onthe contrary a variety of optional components are described toillustrate the wide variety of possible embodiments of the presentinvention.

When a single device or article is described herein, it will be readilyapparent that more than one device/article (whether or not theycooperate) may be used in place of a single device/article. Similarly,where more than one device or article is described herein (whether ornot they cooperate), it will be readily apparent that a singledevice/article may be used in place of the more than one device orarticle or a different number of devices/articles may be used instead ofthe shown number of devices or programs. The functionality and/or thefeatures of a device may be alternatively embodied by one or more otherdevices which are not explicitly described as having suchfunctionality/features. Thus, other embodiments of the present inventionneed not include the device itself.

The foregoing description of various embodiments of the invention hasbeen presented for the purposes of illustration and description. It isnot intended to be exhaustive or to limit the invention to the preciseform disclosed. Many modifications and variations are possible in lightof the above teaching. It is intended that the scope of the invention belimited not by this detailed description, but rather by the claimsappended hereto. The above specification, examples and data provide acomplete description of the manufacture and use of the composition ofthe invention. Since many embodiments of the invention can be madewithout departing from the spirit and scope of the invention, theinvention resides in the claims herein after appended.

What is claimed is:
 1. A method, comprising operations of a processor ina storage controller in a storage system of a computing system having ahost and the storage system, the processor operations comprising:receiving by the storage controller of the storage system, a command toperform data processing of data stored within a first storage unitcontrolled by the storage controller; and in response to the dataprocessing command: reading metadata from a storage unit data structurefor the first storage unit storing data in data units of the firststorage unit; based upon read metadata, classifying data units of thefirst storage unit as one of data set-allocated data units allocated toone or more data sets, and unallocated data units unallocated to anydata set, and classifying data set-allocated data units as one of datacontaining data set-allocated data units, and empty data set-allocateddata units; data processing data contained by data containing dataset-allocated data units of the storage unit; and bypassing dataprocessing of the empty data set-allocated data units of the firststorage unit.
 2. The method of claim 1 wherein the data processingincludes at least one of copying, moving, migrating, mirroring,synchronizing and resynchronizing data of the first storage unit withrespect to a second storage unit of the storage system.
 3. The method ofclaim 1 wherein the storage unit is a volume of storage and the storageunit data structure storing the metadata includes a volume table ofcontents data structure.
 4. The method of claim 3 wherein the data unitof a volume is an extent and wherein the metadata of the volume table ofcontents data structure includes metadata identifying data set-allocatedextents of the volume, which have been allocated to a data set, andmetadata identifying unallocated extents of the volume, which have notbeen allocated to a data set.
 5. The method of claim 4 wherein themetadata of the volume table of contents data structure further includesmetadata identifying a boundary between data containing dataset-allocated extents of a data set of the volume, and empty dataset-allocated extents of a data set of the volume, which lack data ofthe data set.
 6. The method of claim 5 wherein the classifying dataset-allocated data units as one of data containing data set-allocateddata units, and empty data set-allocated data units, is a function ofthe metadata identifying data set-allocated extents of the volume, whichhave been allocated to a data set, and metadata identifying a boundarybetween data containing data set-allocated extents of a data set of thevolume, and empty data set-allocated extents of a data set of thevolume, which lack data of the data set.
 7. The method of claim 3further comprising bypassing data processing of the empty dataset-allocated data units of the first storage unit, wherein a data unitof a volume is an extent and wherein the metadata of the volume table ofcontents data structure includes metadata identifying data set-allocatedextents of the volume, which have been allocated to a data set, andmetadata identifying unallocated extents of the volume, which have notbeen allocated to a data set, and metadata identifying a location of adata set containing a volume record which contains a relative byteaddress identifying a boundary between data containing dataset-allocated extents of a data set of the volume, and empty dataset-allocated extents of a data set of the volume, which lack data ofthe data set, and wherein the classifying data set-allocated data unitsas one of data containing data set-allocated data units, and empty dataset-allocated data units, is a function of the metadata identifying dataset-allocated extents of the volume, which have been allocated to a dataset, and metadata identifying the relative byte address identifying aboundary between data containing data set-allocated extents of a dataset of the volume, and empty data set-allocated extents of a data set ofthe volume, which lack data of the data set.
 8. A computer programproduct for providing a storage management system to manage dataprocessing in a storage controller in a storage system of a computingsystem having a host and the storage system wherein the storage systemincludes a storage unit controlled by the storage controller, andwherein the computer program product comprises a computer readablestorage medium having program instructions embodied therewith, theprogram instructions executable by a processor of the storage managementsystem to cause operations, the operations comprising: receiving by thestorage controller of the storage system, a command to perform dataprocessing of data stored within a first storage unit controlled by thestorage controller; and in response to the data processing command:reading metadata from a storage unit data structure for the firststorage unit storing data in data units of the first storage unit; basedupon read metadata, classifying data units of the first storage unit asone of data set-allocated data units allocated to one or more data sets,and unallocated data units unallocated to any data set, and classifyingdata set-allocated data units as one of data containing dataset-allocated data units, and empty data set-allocated data units; dataprocessing data contained by data containing data set-allocated dataunits of the storage unit; and bypassing data processing of the emptydata set-allocated data units of the first storage unit.
 9. The computerprogram product of claim 8 wherein the data processing includes at leastone of copying, moving, migrating, mirroring, synchronizing andresynchronizing data of the first storage unit with respect to a secondstorage unit of the storage system.
 10. The computer program product ofclaim 8 wherein the storage unit is a volume of storage and the storageunit data structure storing the metadata includes a volume table ofcontents data structure.
 11. The computer program product of claim 10wherein the data unit of a volume is an extent and wherein the metadataof the volume table of contents data structure includes metadataidentifying data set-allocated extents of the volume, which have beenallocated to a data set, and metadata identifying unallocated extents ofthe volume, which have not been allocated to a data set.
 12. Thecomputer program product of claim 11 wherein the metadata of the volumetable of contents data structure further includes metadata identifying aboundary between data containing data set-allocated extents of a dataset of the volume, and empty data set-allocated extents of a data set ofthe volume and lacking data of the data set.
 13. The computer programproduct of claim 12 wherein the classifying data set-allocated dataunits as one of data containing data set-allocated data units, and emptydata set-allocated data units, is a function of the metadata identifyingdata set-allocated extents of the volume, which have been allocated to adata set, and metadata identifying a boundary between data containingdata set-allocated extents of a data set of the volume, and empty dataset-allocated extents of a data set of the volume, which lack data ofthe data set.
 14. The computer program product of claim 10 furthercomprising bypassing data processing of the empty data set-allocateddata units of the first storage unit, wherein a data unit of a volume isan extent and wherein the metadata of the volume table of contents datastructure includes metadata identifying data set-allocated extents ofthe volume, which have been allocated to a data set, and metadataidentifying unallocated extents of the volume, which have not beenallocated to a data set, and metadata identifying a location of a dataset containing a volume record which contains a relative byte addressidentifying a boundary between data containing data set-allocatedextents of a data set of the volume, and empty data set-allocatedextents of a data set of the volume, which lack data of the data set,and wherein the classifying data set-allocated data units as one of datacontaining data set-allocated data units, and empty data set-allocateddata units, is a function of the metadata identifying data set-allocatedextents of the volume, which have been allocated to a data set, andmetadata identifying the relative byte address identifying a boundarybetween data containing data set-allocated extents of a data set of thevolume, and empty data set-allocated extents of a data set of thevolume, which lack data of the data set.
 15. A computing system for usewith a host, comprising: a storage system having at least one storageunit for storing data in data units, the storage system further having aserver having a storage controller having a storage management systemconfigured to control the at least one storage unit and to manage dataprocessing in the storage system and having at least one processor and acomputer program product, wherein the computer program product comprisesa computer readable storage medium having program instructions embodiedtherewith, the program instructions executable by a processor of thestorage management system to cause operations, the operationscomprising: receiving by the storage controller of the storage system, acommand to perform data processing of data stored within a first storageunit controlled by the storage controller; and in response to the dataprocessing command: reading metadata from a storage unit data structurefor the first storage unit storing data in data units of the firststorage unit; based upon read metadata, classifying data units of thefirst storage unit as one of data set-allocated data units allocated toone or more data sets, and unallocated data units unallocated to anydata set, and classifying data set-allocated data units as one of datacontaining data set-allocated data units, and empty data set-allocateddata units; data processing data contained by data containing dataset-allocated data units of the storage unit; and bypassing dataprocessing of the empty data set-allocated data units of the firststorage unit.
 16. The computing system of claim 15 wherein the dataprocessing includes at least one of copying, moving, migrating,mirroring, synchronizing and resynchronizing data of the first storageunit with respect to a second storage unit of the storage system. 17.The computing system of claim 15 wherein the storage unit is a volume ofstorage and the storage unit data structure storing the metadataincludes a volume table of contents data structure.
 18. The computingsystem of claim 17 wherein the data unit of a volume is an extent andwherein the metadata of the volume table of contents data structureincludes metadata identifying data set-allocated extents of the volume,which have been allocated to a data set, and metadata identifyingunallocated extents of the volume, which have not been allocated to adata set.
 19. The computing system of claim 18 wherein the metadata ofthe volume table of contents data structure further includes metadataidentifying a boundary between data containing data set-allocatedextents of a data set of the volume, and empty data set-allocatedextents of a data set of the volume, which lack data of the data set.20. The computing system of claim 19 wherein the classifying dataset-allocated data units as one of data containing data set-allocateddata units, and empty data set-allocated data units, is a function ofthe metadata identifying data set-allocated extents of the volume, whichhave been allocated to a data set, and metadata identifying a boundarybetween data containing data set-allocated extents of a data set of thevolume, and empty data set-allocated extents of a data set of thevolume, which lack data of the data set.
 21. The computing system ofclaim 17 further comprising bypassing data processing of the empty dataset-allocated data units of the first storage unit, wherein a data unitof a volume is an extent and wherein the metadata of the volume table ofcontents data structure includes metadata identifying data set-allocatedextents of the volume, which have been allocated to a data set, andmetadata identifying unallocated extents of the volume, which have notbeen allocated to a data set, and metadata identifying a location of adata set containing a volume record which contains a relative byteaddress identifying a boundary between data containing dataset-allocated extents of a data set of the volume, and empty dataset-allocated extents of a data set of the volume, which lack data ofthe data set, and wherein the classifying data set-allocated data unitsas one of data containing data set-allocated data units, and empty dataset-allocated data units, is a function of the metadata identifying dataset-allocated extents of the volume, which have been allocated to a dataset, and metadata identifying the relative byte address identifying aboundary between data containing data set-allocated extents of a dataset of the volume, and empty data set-allocated extents of a data set ofthe volume, which lack data of the data set.